T-attenuator or coupling network having an identical characteristic impedance from either end

ABSTRACT

An attenuator or pad device which has an outer conductor in the form of a generally T-shaped body, formed with an interior cavity extending longitudinally therethrough. The cavity is also generally T-shaped in configuration having one part in the form of a double-ended expotential horn having its apex or smallest diameter at the center of the tubular body and extending continuously expotentially outwardly therefrom in opposed longitudinal directions to the outer ends of said body. A second part of the cavity forming the stem thereof is also generally expotential in form extending from the bottom of said stem outwardly and upwardly to communicate with the double-ended cavity part at its center. An elongated resistance element defining the inner conductor of the attenuator or pad extends centrally through the cavity and provides an impedance pad which has the same input and output magnitude whereby the device may be utilized as an interstage coupling device.

United States Patent Barth [451 May 23., 1972 [54] T-A'ITENUATOR ORCOUPLING NETWORK HAVING AN IDENTICAL CHARACTERISTIC IMPEDANCE FROMEITHER END 52 us. 01., ..333/s1 A, 333/34 of Radio Research Lab. Harvardu., McGrawl-lill, 1947, pp. 1,01 s 1,020.

Primary Etaminer-Herman Karl Saalbach Assistant Examiner-Wm. H. PunterAttomey-Baldwin, Egan, Walling & Fetzer ABSTRACT An attenuator or paddevice which has an outer conductor in the form of a generally T-shapedbody, formed with an interior cavity extending longitudinallytherethrough. The cavity is also generally T-shaped in configurationhaving one part in the fon'n of a double-ended expotential horn havingits apex or new ofs h smallest diameter at the center of the tubularbody and extending continuously expotentially outwardly therefrom in op-56] Reerences Cited posed longitudinal directions to the outer ends ofsaid body.

Asecond part of the cavity forming the stem thereof is also UNITEDSTATES PATENTS' generally expotential in form extending from the bottomof 2,399,645 5 1946 Latimer ..333/34 x said Stein outwardly and lq y tocommunicate with the 2,620,396 12/1952 Johnson et al ...333/81 Adouble-ended cavity p at Its center- An elongated resistance elementdefining the inner conductor 4:123 3/1965 F 333/81 A of the attenuatoror pad extends centrally through the cavity I 5 6 3/1967 g 333/81 andprovides an impedance pad which has the same input and y outputmagnitude whereby the device may be utilized as an in- OTHERPUBLICATIONS terstage coupling device.

Harvard, Very High Frequency Techniques, Vol. 2, Staff '1 Claims, 2Drawing Figures 24 I /0 24a 4 [a t4 t2 1 QWXXXX Patented May 23, 19723,665,347

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HTTORNEYfi T-ATTENUATOR OR COUPLING NETWORK HAVING AN IDEN'IICALCI'IARACTERIS'I'IC IMPEDANCE FROM EITHER END Additional objects andadvantages of the attenuator on. pad

device of the present invention will be apparent to one skilled in theart and upon reference to a preferred embodiment thereof as is describedin the following specification and illustrated in the accompanyingdrawings wherein:

FIG. 1 is a side view in elevation of the attenuator or pad deviceembodying the present invention;

FIG. 2 is an end view taken an approximately of FIG. 1;

FIG. 3 is a longitudinal sectional view taken on line 3--3 of FIG. 2;and v FIG. 4 is a schematic diagram of the effective circuit of theattenuator device.

Referring now to the drawings, as shown particularly in FIGS. 1 and 3,the attenuator or pad device of the present invention includes anelongated tubular body 10 generally T- shaped in overall configurationformed of a suitably conductive material such as steel and definingafirst or cross-bar part 12 and a second or stem part 14.

The first body part 12 is provided with an internal cavity 16 whichextends generally centrally longitudinally therethrough, and is of adouble-ended expotential horn configuration. The apex 17 of thehorn-type cavity is located at the center of the body 10, the wallthereof extending expotentially outwardly toward the opposedlongitudinal ends to an end cavity portion 18 of constant diameter.

The stem part 14 of the body 10 is also formed with an internal cavityas shown at 20 which extends centrally longitudinally therethrough beingsingle-end expotential horn-like in configuration with the wide end ofthe horn communicating with the apex 17 of the aforesaid horn cavity 16.

A suitable resistance element, being generally tubular in form asidentified at R, and which may be made of any suitable material merelyfor example a ceramic base material having a resistance materialdeposited on the surface thereof, maybe disposed in the cavity 16extending centrally therethrough being thus equally spaced from thecavity wall.

As seen at 22, end caps formed of any suitable insulating the line 2-2material may be disposed in the end cavity portions 18 and into whichthe ends of said resistance element R may be disposed being thuseffective to retain the same centrally within the cavity 16.

A second resistance element as identified at T may be similarly disposedin the cavity 20 of the body part 14, an end thereof projecting into theapex part 17 of the horn cavity 16 and suitably rigidly attached to theresistance element R at its center point.

The stem part 14 of the body 10 is provided with an upstanding rim 24surrounding the adjacent end of the cavity 20 and provides support forthe end of the resistance element T disposed therein.

The resistance material is deposited by any suitable method upon thesurface of the rod elements R and T being distributed thereover andconnected together at the juncture of the said. rod elements to form aT-network comprising resistances R, and R: as shown in FIG. 4.

The stem part of the body may be threaded as seen at 240 which mayenable a suitable cap 26 to be placed thereover. to effectively seal thecavity 20 at said one end. The body of the device may also be providedwith a threaded port 28 which opens to the apex 17 of the horn cavity 16directly opposite the communicatin end of cavity 20, and which may beused ly of the device and connection thereof to facilitate assem into anelectronic circuit.

The input end of the attenuator or pad device may be terminals t and tand the output end similarly identified at t, and By attachingconductors to each of said terminals 1, and tgand connecting rg, to thebody 10, the attenuator or pad device may be used as an interstagecoupler; terminals 2, and representing the input of said attenuator andterminals and t the output thereof. Terminal i may be used as thecircuit ground or neutral conductor. The resistance elements R and Twith the aforesaid terminal connections defines the inner conductor ofthe attenuator or pad, and the body 10 the outer conductor of saiddevice.

With the resistance values R, and R assigned, it will also be i realizedthat the characteristic impedance 2,, looking in either As is furtherunderstood, the inductance of the attenuato or pad varies directly asthe logarithm of the spacing between the center conductor R R and thebody 10 representing the outer conductor the wall of cavity 16 varyingexpotentially and decreasing in spacing toward the apex 17. Likewise,the capacitance varies inversely as the logarithm of the aforesaidspacing between said conductors. In like manner, the inductance of thesection of the pad represented by resistance R in the stem cavity 20varies directly as the logarithm of the spacing between the centerconductor R and the wall defining said cavity 20 which is seen to varyexpotentially from the apex 17 of horn cavity 16 and decreasing to theupper end thereof as seen in FIG. 3. Also, the capacitance of this padsection varies inversely as the logarithm of the aforesaid spacingbetween said conductors.

Having thus described a preferred embodiment of attenuator or pad deviceof the present invention, it will be apparent to one skilled in the artto which it pertains that this invention may be changed and/or modifiedwithout departing from the inventive concept as are defined in theclaims.

What is claimed is:

1. An attenuator or pad for providing interstage coupling comprising abody formed of conductive material, means defining a double-endedexpotential horn in said body and extending longitudinally therethroughwith the apex of said horn being at the center of the body, means insaid body defining a single-ended expotential horn extendingtransversely of the double-ended horn and connecting at its larger endwith the apex of the double-ended horn, first resistance means extendingcentrally through the double-ended horn, second resistance meansextending centrally through the single-ended horn, one end of the secondresistance means connecting with the first resistance means at the apexof the double-ended horn to thereby form a T-network having a shuntresistor and two series resistors equal to each other, the opposite endof the shunt resistor being defined as the common terminal of theT-network, the free end of each of the series resistors representing aninput tenninal and an output terminal respectively of said T-networkwhich together with the common terminal define the input end and theoutput end of the network, the impedance of each series resistor of theT-network as determined by the spacing between the series resistor andits associated surrounding wall of the double-ended horn varyingexpotentially and in a decreasing magnitude incrementally

1. An attenuator or pad for providing interstage coupling comprising abody formed of conductive material, means defining a double-endedexpotential horn in said body and extending longitudinally therethroughwith the apex of said horn being at the center of the body, means insaid body defining a singleended expotential horn extending transverselyof the double-ended horn and connecting at its larger end with the apexof the double-ended horn, first resistance means extending centrallythrough the double-ended horn, second resistance means extendingcentrally through the single-ended horn, one end of the secondresistance means connecting with the first resistance means at the apexof the double-ended horn to thereby form a T-network having a shuntresistor and two series resistors equal to each other, the opposite endof the shunt resistor being defined as the common terminal of theT-network, the free end of each of the series resistors representing aninput terminal and an output terminal respectively of said T-networkwhich together with the common terminal define the input end and theoutput end of the network, the impedance of each series resistor of theT-network as determined by the spacing between the series resistor andits associated surrounding wall of the double-ended horn varyingexpotentially and in a decreasing magnitude incrementally equally towardthe apex of the horn and the impedance of the shunt resistor of theT-network as determined by the spacing between said shunt resistor andits associated surrounding wall of the single-ended horn varyingexpotentially and in an increasing magnitude incrementally toward theapex whereby the T-network has an identical characteristic impedancefrom either end.